In the field of medical science, pulmonary arterial hypertension (PAH) is a heart/lung disorder in which the blood pressure in the pulmonary arteries and/or pulmonary arterioles far exceeds normal levels. The precise causes of PAH are still not completely known. PAH manifests in the form of shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by physical exertion and stress. Pulmonary hypertension can be a severe disease with a markedly decreased exercise tolerance and can result in heart failure, and eventually death, for some patients.
The electrocardiogram (ECG or EKG) complex is defined by a plurality of waves, segments, and intervals as follows. The P-wave is the first component of the ECG complex and corresponds to atrial depolarization (contraction). It is usually a positive deflection from the baseline. The QRS complex corresponds with ventricular depolarization (contraction) and is measured from the beginning of the Q-wave or R-wave (if no Q-wave is present) to the end of the S-wave. The normal duration of the QRS complex is 0.04-0.11 seconds. The Q-wave is the first negative deflection of the QRS complex. The R-wave is the first positive deflection of the complex. The S-wave is the negative deflection following the R-wave. Not every QRS complex has a Q, R, and S-wave. The T-wave corresponds with ventricular repolarization (relaxation). The U-wave is a small wave of low voltage and, if present, follows the T-wave. The PR segment begins at the end of the P-wave and continues until the beginning of the QRS complex. The PR interval includes the P-wave and PR segment. The normal PR interval measurement is 0.12-0.20 seconds. The ST segment is measured from the end of the QRS complex to the beginning of the T-wave. The QT interval corresponds with ventricular depolarization (contraction) and repolarization (relaxation). The normal QT interval measurement is 0.32-0.40 seconds.